For the first time since it began keeping records, 47 years ago, UNICEF has determined that the number of annual deaths among young children has fallen below 10 million. Last year, 9.7 million children around the world died before reaching age 5, down from about 20 million in 1960. Among the chief reasons for the drop, UNICEF officials said, were increased vaccinations; wider use of mosquito netting and anti-malarial measures; and the growing popularity of breast-feeding in place of formulas that often are mixed with polluted water. “We feel we’re at a tipping point now,” said UNICEF’s chief medical officer, Dr. Peter Salama. “In a few years’ time, it will all translate into a very exciting drop.”